Fractographic Analysis Research Articles

Temperature-dependent liquid metal embrittlement of Al0.7CoCrFeNi high-entropy alloys induced by equiatomic GaInSnZn melts

The equiatomic GaInSnZn (GISZ) high-entropy alloys (HEAs) are considered to have the potential as coolants to engage the thermal management owing to their high thermal conductivity. However, the incompatibility between them and other structural materials hinders these practical applications. On the way to seeking suitable structural metals with liquid metal embrittlement (LME) resistance in GISZ environment, the Al0.7CoCrFeNi alloys are selected and their temperature-dependent LME sensitivity is investigated through high temperature and slow strain-rate tensile tests at 100, 300 and 500 ℃. The sharp decrease in tensile ductility and serious LME phenomenon are explicitly inspected at all temperatures. The transformation of the LME mechanism, which shifts from adsorption-induced reduction in cohesion of the interior or boundaries of grain colonies to grain/phase boundary wetting with temperature increasing, is corroborated by the fractographic analysis and crack propagation path. This study not only provides guidance for the LME of this new system, but also encourages a promising landscape for searching for protective measures of Al0.7CoCrFeNi alloys and new materials adapted to GISZ, thereby laying a solid foundation for promoting liquid metal cooling applied to the actual industry.

Hydrophobic electroless nickel phosphorus-graphene carbon nitride coating on AISI 4140 steel with enhanced hardness and scratch resistance

The present article explores the ability of synthesized graphene carbon nitride (g-C3N4) towards the improvement of microstructure, surface energy, surface hardness, and scratch resistance of electroless nickel phosphorus-graphene carbon nitride (NiP/g-C3N4) coated AISI 4140 steel. Comparative studies were conducted to evaluate how the g-C3N4 concentrations affect the physical, mechanical, and surface properties of electroless NiP/g-C3N4 composite coating. Morphology analysis confirmed the nodular formation for the NiP/g-C3N4 composite coating due to the nucleation phenomenon induced by the g-C3N4 particle. Further, the g-C3N4 particle has favoured the growth of the Ni crystal, which is confirmed in the X-ray diffractometer study. In comparison, the higher weight percentage of g-C3N4 particles has increased the hardness, residual stress, surface roughness, and contact angle of the electroless NiP/g-C3N4 composite coating. The maximum tensile residual stress had a positive impact on controlling the formation of slippage cracks for the NiP/g-C3N4 composite coating, which is confirmed in the fractography analysis of the hardness indentation. Furthermore, the detailed failure mechanisms of the coatings during the hardness and scratch test of NiP/g-C3N4 composite coatings were precisely discussed and compared with the particle-free NiP coating.

Statistical-based optimization of fused filament fabrication parameters for short-carbon-fiber-reinforced poly-ether-ether-ketone considering multiple loading conditions

Fused filament fabrication (FFF) is one of the most widely used additive manufacturing processes and allows the production of complex parts. FFF can manufacture lightweight and strong structural components when processing high-performance carbon-fiber-reinforced thermoplastics. Although the process feasibility for printing 20% short-carbon-fiber reinforced PEEK was already demonstrated in the literature, a systematic study addressing the influence of printing parameters on different loading conditions is still lacking. Therefore, the present study investigates the influence of selected FFF parameters – i.e., layer height (LH), printing temperature (PT) and printing speed (PS) – on three mechanical properties: tensile (UTS), bending (UBS), and impact (UIS) ultimate strengths. The analyzed samples were printed and tested according to a central composite design of experiments, and each parameter's individual and combined effects were assessed by analysis of variance (ANOVA). Different regression models were obtained for each test, allowing the optimization of the parameters for each condition and resulting in three distinct optimized parameter sets. The relationship between parameters and microstructure was also assessed via fractography analyses, showing that lower LH and PS reduce the number and size of volumetric defects observed within the printed parts, as lower values improve interlayer cohesion. Contrarily, PT showed that average values (around 385 °C) benefit the microstructure the most, as higher temperatures result in larger defects and low temperatures reduce interlayer cohesion. Finally, the contour plots of the three produced models were overlaid to identify a universal parameter set capable of simultaneously correlating and maximizing all three performances. This procedure allowed the identification of the following optimized values: LH of 0.1 mm, PT of 385 °C and PS of 17.5 mm/s, resulting in the experimental UTS, UBS and UIS values of 116.7 ± 5 MPa, 167.2 ± 11 MPa and 28.2 ± 3 kJ/m2.

Effect of denture cleansers on the physical and mechanical properties of CAD-CAM milled and 3D printed denture base materials: An in vitro study

Statement of problemStudies on the impact of denture cleansers on the physical and mechanical properties of denture bases designed and constructed by using computer software programs are lacking. PurposeThe purpose of this in vitro study was to test the effect of a peroxide denture cleanser on the hardness, fracture toughness, water sorption, and solubility of denture base materials manufactured by 3D printing and computer-aided design and computer-aided manufacturing (CAD-CAM) milling. Material and methodsThe hardness, fracture toughness, water solubility, and sorption of CAD-CAM milled and 3D printed groups (n=40) were evaluated before and after exposure to a denture cleanser. Hardness (n=10) was analyzed with a Vickers hardness testing machine, and fracture toughness (n=20) with the 3-point bend test. After the fracture of specimens, a scanning electron microscope at ×300 was used for fractographic analysis. Water sorption and solubility (n=10) were evaluated before and after immersion in denture cleanser for 6 days to simulate 180 days of immersion. Two-way repeated ANOVA and 2-way ANOVA were used to test normally distributed data, whereas the Mann Whitney U test and Wilcoxon signed ranks test were used for data that were not normally distributed (α<.05). ResultsThe Vickers hardness and fracture toughness of both materials decreased after immersion in denture cleansers, with a higher decrease in values for the 3D printed group (P<.001). The denture cleanser had no effect on the water sorption and solubility of either group. ConclusionsMilled specimens had higher hardness values and fracture toughness before and after immersion in the denture cleanser. Denture cleansers resulted in the reduced hardness and fracture toughness of both groups, but the percentage change in the milled group was lower. Denture cleansers had no effect on water sorption or solubility.

Structural and Fractographic Analysis of Aluminum Alloy before and after Fatigue Loading

Structural and Fractographic Analysis of Aluminum Alloy before and after Fatigue Loading

Effect of ECAP on fracture toughness and fatigue endurance of DED-processed Ti-6Al-4V investigated on miniaturized specimens

Additive manufacturing (AM) has revolutionised the production of complex components with custom mechanical properties. However, as-deposited AM-ed materials often exhibit inferior mechanical behaviour compared to conventionally manufactured counterparts because of defects generated during the deposition. In this study, the effects of equal channel angular pressing (ECAP) on fracture toughness and fatigue endurance of Ti-6Al-4V titanium alloy manufactured by direct energy deposition (DED) are investigated. The aim of this study is to compare the mechanical performance of the material in the as-deposited and ECAP-ed states, exploiting the potential benefits of ECAP in improving the properties of additively manufactured components. ECAP processing is used to induce severe plastic deformation (SPD) and create a unique microstructure in Ti-6Al-4V specimens. As-deposited and ECAP-ed specimens were evaluated using stress intensity factor (SIF) analysis, fatigue crack growth, and high cycle fatigue tests using miniaturized specimens. Fractographic analysis was performed using scanning electron microscopy (SEM) to examine the fracture surfaces and identify the underlying failure mechanisms. The results revealed that while ECAP led to a slight increase in porosity, it significantly reduced fracture toughness and had a negligible effect on the rate of propagation of fatigue cracks. In addition, the ECAP-ed specimens showed reduced fatigue endurance of the material.

Effect of stress triaxiality on the hydrogen embrittlement micromechanisms in a pipeline steel evaluated by fractographic analysis

Hydrogen gas, as an energy carrier, is expected to play an important role in the storage and transport of energy produced by renewable sources. The transport of hydrogen gas can be managed through the use of existing pipeline networks. However, the uptake of hydrogen in steel structures is known to cause a degradation of mechanical properties, a phenomenon called hydrogen embrittlement (HE). In this study, the hydrogen-assisted ductility loss of an API 5L X70 pipeline steel is investigated. The influence of hydrogen on mechanical behavior is evaluated by tensile tests on uncharged and hydrogen charged specimens. These tests are performed on notched round bar specimens with different notch radii, allowing for a range of positive stress triaxialities to be examined. Notched samples are more embrittled than unnotched specimens after hydrogen charging. Hydrogen signatures in the form of fisheyes and quasi-cleavage are detected on the fracture surface. Fisheyes initiate primarily at segregation bands in the steel for all specimen geometries. Fisheyes can also be linked to different inclusion types present in the steel, depending on notch geometry. For unnotched as well as the least sharply notched specimens tested in this study, the embrittlement can be correlated with the area fraction of fisheyes on the fracture surface.

A comparative evaluation of fracture resistance of tooth restoration complex restored with PEEK and lithium disilicate endocrowns.

This in vitro study was conducted to compare the fracture resistance of tooth restoration complex restored with polyetheretherketone (PEEK) and lithium disilicate endocrowns. A total of 46 extracted premolars were collected and treated endodontically. The teeth were mounted in cylindrical molds using autopolymerizing resin and were prepared for endocrown restoration. Specimens were divided into two groups (n = 23) to receive endocrowns made with two different materials (polyetheretherketone and lithium disilicate). All the specimens were subjected to thermal cycling. The fracture resistance test was carried out using a Universal Testing Machine. Fractographic analysis was carried out using stereomicroscope and scanning electron microscope after load test. The values obtained were subjected to statistical analysis. Intergroup comparison (two groups) was performed using a t-test. Comparison of frequencies of categories of variables with groups was performed using chi-square test. Fracture resistance tests showed a statistically significant difference in values between the two groups (p<0.01). High fracture resistance values were seen with lithium disilicate endocrowns. Failure mode analysis showed that both groups exhibited mainly catastrophic failure. There were no significant differences in frequencies of the type of fracture between the groups. The fracture resistance of endocrowns fabricated with lithium disilicate material was found to be significantly higher than polyetheretherketone (PEEK) material. Hence, lithium disilicate material is superior for endocrowns.

Ultrathin lithium disilicate and translucent zirconia crowns for posterior teeth: Survival and failure modes.

To evaluate the reliability and failure modes of ultrathin (0.5 mm) lithium disilicate, translucent and ultra-translucent zirconia crowns for posterior teeth restorations. Fifty-four mandibular first molar crowns of three ceramic materials: (1) Lithium disilicate (e.max CAD, Ivoclar Vivadent), (2) 3Y-TZP (Zirconn Translucent, Vipi), and (3) 5Y-PSZ (Cercon XT, Dentsply Sirona), with 0.5 mm of thickness were milled and cemented onto composite resin abutments. Eighteen samples of each group were tested under mouth-motion step-stress accelerated life testing in a humid environment using mild, moderate, and aggressive profiles. Data was subjected to Weibull statistics. Use level curves were plotted and reliability was calculated for a given mission of 100,000 cycles at 100, 200, and 300 N. Fractographic analyses of representative samples were performed in scanning electron microscope. Beta (β) values suggest that failures were dictated by material's strength for lithium disilicate and by fatigue damage accumulation for both zirconias. No significant differences were detected in Weibull modulus and characteristic strength among groups. At a given mission of 100,000 cycles at 100 N, lithium disilicate presented higher reliability (98% CB: 95-99) regarding 3Y-TZP and 5Y-PSZ groups (84% CB: 65%-93% and 79% CB: 37&-94%, respectively). At 200 N, lithium disilicate reliability (82% CB: 66%-91%) was higher than 5Y-PSZ (20% CB: 4%-44%) and not significantly different from 3Y-TZP (54% CB: 32%-72%). Furthermore, at 300 N no significant differences in reliability were detected among groups, with a notable reduction in the reliability of all materials. Fractographic analyses showed that crack initiated at the interface between the composite core and the ceramic crowns due to tensile stress generated at the intaglio surface. Ultrathin lithium disilicate crowns demonstrated higher reliability relative to zirconia crowns at functional loads. Lithium disilicate and zirconia crown's reliability decreased significantly for missions at higher loads and similar failure modes were observed regardless of crown material. The indication of 0.5 mm thickness crowns in high-load bearing regions must be carefully evaluated. Ultraconservative lithium disilicate and zirconia crowns of 0.5 mm thickness may be indicated in anterior restorations and pre-molars. Their clinical indication in high-load requirement regions must be carefully evaluated.

Influence of mean stress and overaging on fatigue life of aluminum alloy EN AW-2618A

Fatigue tests were performed on the forged aluminum alloy EN AW-2618A in the T61 state. Different stress ratios (R = −1, R = 0.1) were selected to study the influence of mean stress on fatigue life. Two overaged states (10 h/230 °C, 1000 h/230 °C) were also tested to investigate the influence of overaging on fatigue life. Transmission electron microscopy (TEM) was used to characterize the precipitates (S-phase), which are mainly responsible for the strength of the alloy. A fractographic analysis was also performed to determine the failure mode. Overaging reduces the fatigue life compared to the T61 state. The longer the aging time, the lower the fatigue resistance. The reason is the decrease in (yield) strength, which correlates with the radius of the S-phase: the precipitate radius increases by a factor of approximately two for the overaged states compared to the initial state. The analysis of the fracture surfaces showed crack initiation occurs predominantly on the outer surface and is associated with the primary phases.

Fatigue life assessment and fracture mechanisms of additively manufactured metal-fiber reinforced thermoplastic hybrid structures produced via ultrasonic joining

Ultrasonic Joining (U-Joining) produces through-the-thickness reinforced (TTR) hybrid joints between thermoplastics and surface-structured metals. The joining parameters were previously optimized to join additively manufactured (AM) 316L stainless steel (316L SS) and 20% short-carbon-fiber-reinforced poly-ether-ether-ketone (PEEK-20CF) to maximize the joints' performance under quasi-static lap shear testing. However, further investigations on the joint's fracture mechanisms and cyclic loading performance are still lacking. Therefore, this study describes the stress distributions, assesses the fracture mechanisms and evaluates the fatigue life of AM 316L SS/PEEK-20CF hybrid joints. A finite element model was developed to clarify the joints' mechanical behavior, and their fatigue performance was assessed under cyclic tensile condition. The fatigue tests were performed at different percentages of the reached ultimate lap shear force (ULSF) and analyzed via two-parameter Weibull distribution and load-life curves for different reliability levels. The results showed that a fatigue life of 1 × 106 cycles could be reached when a load of 1.52 kN, or 42% of the ULSF, is applied, demonstrating the joints' high mechanical performance and potential for engineering applications. Joints reaching the one million cycles threshold were stopped at this mark and tested under quasi-static lap shear to assess their residual force. The results significantly decreased from 3.6 ± 0.3 kN to 2.4 ± 0.5 kN for ULSF and residual force, respectively. Fractography analyses identified polymer delamination, partial TTR pull-out, and interfacial/net-tension failure as the main fracture mechanisms. Polymer detachment in fatigue specimens indicated the influence of secondary bending at low load levels, explaining the reduced residual force.

Mechanical Properties and Microstructure of Dissimilar S355/AA6061-T6 FSW Butt Joints.

The aim of this paper is to analyse the mechanical properties of butt joints between S355 steel and 6061-T6 aluminium alloy, as well as their relationship to changes in the structure of the material caused by welding. The effect of the tool offset was analysed in particular. For the analysis, tensile tests were carried out using macro- and mini-specimens taken from S355/AA6061-T6 joints and base materials. In addition, the macro- and microstructure of the joints was determined, the hardness profiles in the joints were analysed, and fractographic analysis of the fractures of the specimens was carried out. Based on the results of the macro- and microstructure examinations, typical friction stir welding (FSW) joint zones were characterised. The microstructure was observed in the interface line of the materials on the root side, the negative effect of which on the quality of the joint was confirmed by digital image correlation (DIC) strain analysis during the monotonic tensile test. The highest average value of su = 141 MPa for the entire joint was obtained for a 0.4 mm tool offset. The highest average value of su = 185 MPa for the selected joint layer was obtained for a 0.3 mm tool offset. Fracturing of the joint in the selected layer for the tool offset values of 0.3 mm and 0.4 mm occurred in the weld nugget zone (WNZ) where the lowest hardness was recorded.

Reliability and Failure Mode of Ti-Base Abutments Supported by Narrow/Wide Implant Systems.

To assess the reliability and failure modes of Ti-base abutments supported by narrow and wide-diameter implant systems. Narrow (Ø3.5 × 10 mm) and wide (Ø5 × 10 mm) implant systems of two different manufacturers with internal conical connections (16°) and their respective Ti-base abutments (3.5 and 4.5 mm) were evaluated. Ti-base abutments were torqued to the implants, standardized metallic maxillary incisor crowns were cemented, and step stress accelerated life testing of eighteen assemblies per group was performed in three loading profiles: mild, moderate, and aggressive until fracture or suspension. Reliability for missions of 100,000 cycles at 100 and 150 N was calculated, and fractographic analysis was performed. For missions at 100 N for 100,000 cycles, both narrow and wide implant systems exhibited a high probability of survival (≥99%, CI: 94-100%) without significant differences. At 150 N, wide-diameter implants presented higher reliability (≥99%, CI: 99-100%) compared to narrow implants (86%, CI: 61-95%), with no significant differences among manufacturers. Failure mode predominantly involved Ti-base abutment fractures at the abutment platform. Ti-base abutments supported by narrow and wide implant systems presented high reliability for physiologic masticatory forces, whereas for high load-bearing applications, wide-diameter implants presented increased reliability. Failures were confined to abutment fractures.

Investigations on microstructure and mechanical properties on LM30-B4C nanocomposites fabricated through ultrasonic-squeeze assisted stir-casting

In this work, Aluminium-Silicon grade LM30 nanocomposites were fabricated through ultrasonic squeeze-assisted stir casting. Five formulations were made by varying the weight percentage of Boron Carbide nanoparticles (nB4C) from 0 to 2.0 wt% in steps of 0.5 wt%. The formulation's microstructure, hardness, tensile, compression, and impact strength properties were evaluated. X-ray diffraction technique was used to study the presence of aluminium, silicon, and boron carbide compounds. The fractured surfaces from the tensile tests were investigated using FESEM for fractography analysis. The ultrasonic vibration employed during manufacturing aided homogeneous nanoparticle distribution and helped to refine the microstructure. The results indicated that the LM30 nanocomposite with 1 wt% nB4C enhanced the hardness, tensile strength, and compressive strength. Also, adding nB4C particles provided excellent resilience in absorbing the impact energy.

Investigation of the mechanical behavior of FDM processed CFRP/Al hybrid joint at elevated temperatures

This research is focused on investigating the mechanical behavior of Fused Deposition Modeling (FDM) processed CFRP/Al hybrid riveted joints at elevated temperatures. A two-pronged approach was adopted entailing experimental and computational domains. In the experimental thrust, the developed joint was evaluated for its mechanical behavior by employing Digital Image Correlation, micro-XCT, and fractographic analysis. The tensile testing was performed at four different temperatures, i.e., Room Temperature (RT), 50°C, 75°C, and 100 °C. At RT, the joint experienced net-sectioning in the CFRP sheet along with minute secondary bending. Further, distinct failure modes were noticed for each ply orientation where the inherent porosity/voids appeared as the governing factor for the damage progression. Novel constitutive models were developed using accrued strain and change in energy dissipation to estimate the damage progression. The damage accumulation was found to be more uniform in the 0° layer as compared to 90°. Moreover, the 90° layer exhibited a more catastrophic damage pattern toward final failure. At elevated temperatures, a significant reduction in mechanical properties along with a non-uniform warping/bending of the plies was noticed due to viscoelastic behavior change. The computational analysis, having a hierarchical approach, was performed for the validation of the experimental results, and both were found to be in good agreement.

Improving the structural integrity of foam-core sandwich composites using continuous carbon fiber stitching

This study aims to improve the structural integrity of foam-core sandwich structures by embedding carbon-fiber/epoxy stitched reinforcements with fiber-volume fraction (Vf) as high as 55 %. Sandwich panels with 1.5 mm thick carbon fiber skins and 30 mm thick PVC foam-core were stitched with 0, 12 k and 24 k carbon fiber yarns. X-ray computed tomography (CT) was utilized to determine the “as-manufactured” quality of the stitched panels. Flatwise-, edgewise-compression and 3-point bending tests were conducted with in-situ 3D Digital Image Correlation (DIC) to record the deformation and analyze the structure’s mechanical response. It was observed that compared to non-stitched samples - under flatwise compression loading, the reinforced samples with a stitch Vf of 0.34 and 0.55 showed an increase in stiffness and strength by 130 % and 163 %, and 29 % and 53 %, respectively. For edgewise-compression and 3-point bending loading cases, stiffness and strength of stitched samples showed an increase of ∼20 % over the benchmark. Using DIC, X-ray CT and a fractography analysis, the external and internal damage as well as failure mechanisms were evaluated. Analytical solution was employed to understand the parametric influence of the stitch Vf and stitch density per unit area in pursuit of an optimized sandwich structure.

The effect of cyclic loading on the fracture resistance of 3D-printed and CAD/CAM milled zirconia crowns—an in vitro study

ObjectivesThe aim of this study was to evaluate the effect of cyclic mechanical loading on the fracture resistance of 3D-printed zirconia crowns in comparison to milled zirconia crowns.Materials and methodsMonolithic zirconia crowns (n = 30) were manufactured using subtractive milling (group M) and 3D additive printing (group P). Nine samples of each group were fractured under one-time loading while the other 6 samples were subjected to cyclic loading for 1.2 million cycles before being subjected to one-time loading until fracture. Scanning electron microscope (SEM) fractographic analysis was carried out on fractured fragments of representative samples.ResultsThe mean for fracture resistance of group M was 1890 N without cyclic loading and 1642 N after being subjected to cyclic loading, and they were significantly higher than that of group P (1658 N and 1224 N respectively).ConclusionsThe fabrication technique and cyclic loading affect the fracture resistance of zirconia crowns. Although the fracture resistance values for the 3D-printed crowns were lower than those of the milled, still they are higher than the masticatory forces and thus could be considered being clinically acceptable.Clinical relevanceConcerning fracture resistance, 3D-printed crowns can withstand the masticatory forces for the long term without any cracks or failure.

Low cycle fatigue behaviour of wire arc additively manufactured ER70S-6 steel

Wire arc additive manufacturing (WAAM) is a method of 3D printing that is well suited to the cost-sensitive construction industry. Fundamental test data on the mechanical properties of WAAM materials, especially under cyclic loading, are however lacking. To bridge this gap, an experimental study into the low cycle fatigue (LCF) behaviour of WAAM ER70S-6 steel has been conducted and is presented herein. Following quasi-static mechanical and geometric characterisation, a series of as-built and machined coupons was tested in different directions relative to the print layer orientation (θ = 0°, 45° and 90°) under constant amplitude LCF loading, covering a range of strain amplitudes from ±0.2% to ±2.0%. Fractographic analysis of the tested coupons was also performed to assess their failure mechanisms. On the basis of the experimental results, strain-life relationships and cyclic stress-strain curves were derived. The geometric undulations of the as-built coupons resulted in a weakening in the LCF properties, and the weakening effect increased with the loading angle θ and strain amplitude. The cyclic hardening/softening response of the WAAM material varied with the imposed strain amplitudes, while significant non-Masing behaviour was observed.

Unraveling the Cracking Mechanisms of Air Plasma-Sprayed Thermal Barrier Coatings: An In-Situ SEM Investigation

In this research work, real-time three-point bending coupled with the scanning electron microscopy (SEM) technique were used to study the crack formation and growth of air plasma spraying (APS) thermal barrier coatings (TBCs). The acquired micrographs were then used to study the strain fields in the vicinity of the cracking region using digital image correlation (DIC) analysis. Fractography analysis for the fractured regions of the APS coatings was also discussed. Based on real-time observation, it was found that roughness of the coatings’ free surface (e.g., valleys) can promote the initiation of cracks since it acts as stress concentration points. Pores and splats features of the coating microstructure contribute to crack branching and crack path deflection, respectively. The former phenomenon (i.e., crack branching) negatively affects the lifetime of the TBC system as it results in an increased fracture area, while the latter can improve the fracture toughness of the coatings and its durability through improving the coating’s ability to dissipate the energy required for crack propagation.

Experimental Evaluation of KIEAC of a Carbon Steel Using the Pin-Loaded SENT Geometry

Abstract The experimental determination of the threshold stress intensity factor for environment-assisted cracking (KIEAC) is described by several standards, which allow the use of different specimen geometries and methodologies for crack length estimation. In some cases, the combination of structure, specimen size, or both, main loading direction, and crack orientations of the component that need to be characterized limit the use of standardized geometries. Consequently, alternative geometries must be used. In this study, fatigue pre-cracked pin-loaded single edge notched tension specimens as defined by BS 8571:2018, Method of Test for Determination of Fracture Toughness in Metallic Materials Using Single Edge Notched Tension (SENT) Specimens, were applied for the experimental evaluation of the KIEAC of a carbon steel. The specimens were tested in deaerated substitute ocean water solution saturated with carbon dioxide at 40°C and at 1 and 10 bar (100 and 1,000 kPa) under constant load conditions with incremental (step) loading. The crack length during the tests was monitored by direct current potential drop, which was helpful for defining the applied K corresponding to the onset of subcritical crack growth (KIEAC). Additionally, fractographic analysis of KEAC specimens and results from the fracture toughness evaluation of this material in air at room temperature have also been reported.